The invention concerns electronic library services in which machine-executed processes manage collections of data representing books, papers, folders, personal files, and other informational media of durable value. Particularly, the invention covers the inter-process communications which are necessary to manage a library of images in such a way as to provide access to the library while affording security, integrity authentication, and consistency of library data. The term "image" is defined more formally below. Here, and until the definition, an "image" is any digital representation of the contents of a readable medium such as paper.
Digital electronic computers have found growing use in enterprise library services. Such use can benefit from a library service in the form of common session-level, inter-machine protocols. Such protocols are particularly useful in a library of data objects to which a plurality of users may demand concurrent access and which are stored on a plurality of physically and geographically separated storage resources. The isolation of such protocols frees up for separate consideration other aspects of library management including network configuration, resource scheduling, catalog schema, and the representation and meaning of the data objects which the library embraces.
A library service subsystem executable on one or more electronic digital computers might be considered merely a specialized database management system, with a particular choice of data schema and integrity rules. However, the inventors have found that the statistics and circumstances of library use are sufficiently different from those of other database applications to warrant special attention. For example, compared to the records of a traditional database, objects in a library tend to be relatively large, relatively rarely read, very rarely changed, and not directly useful as search indices; to be economical, a library implementation must include an automatic storage hierarchy--a feature which is not found in traditional database management systems. For knowledge workers, it is neither desirable nor possible to predict to which libraries any particular worker will need access; limited only by rules to protect the owners of information, all libraries should be available with a common interface, even across enterprise boundaries.
The creation of a library service subsystem can proceed simply by addition of capabilities to existing database and file servers.
Consequently, there is a manifest need for protocols and control mechanizations directed to the management of access to distributed library data which do not constrain other aspects of library management.